What's the story with rainfall in Ireland so far this year?

We may have had a relatively dry winter, but are we making up for it now and will we see wetter months ahead?

Benjamin Franklin famously said 'nothing can be said to be certain, except death and taxes'. Irish people might want to add ‘and rain’ to the end of that old adage. We love to talk about the rain (or lack of it) and it impacts innumerable facets of people’s lives, from what to wear to when to spray a field (for the farmers among us).

Typically, the narrative around rainfall is that there is just too much of it. Questions start to be raised when it seems that there is less of a requirement for brollies and raincoats than usual, which appeared to be the case this winter. We asked Dr Catriona Duffy, a meteorologist working with Met Éireann, to tell us about what has been going on

It feels like we had less rain this winter than in previous years - is this true?

"When we measure how much wetter or drier a season has been, it is always in comparison with a standard reference period, which in this case is the Long-Term Average (LTA) period from 1981-2010. The meteorological winter of 2022/2023 was indeed drier than others at provisionally 75% of its LTA. In fact, no matter where you are in Ireland, this winter's rainfall was below normal, ranging from 131.4 mm (71% of its LTA) at Dublin Airport to 429.4 mm (91% of the LTA) at Newport, Co. Mayo.

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"To find a drier winter in the recent past, you have to go back to 2010, which was 70% of its LTA (although this was also a winter with significant snowfall). Before that, the two of the driest winters on record occurred in 1963 (58% of its LTA) and 1964 (51% of its LTA). February 2023 was the fifth warmest on record (record length 123 years) and, in terms of rainfall, was fourth driest (record length 83 years). While meteorological winter 2022/2023 was 25th warmest and 17th driest. So to put it in a climate context: yes, this winter has been dry, but we have had drier."

What was the cause of this - or were we lucky?

"'Being lucky' is relative. If you are someone who enjoys the outdoors, then you have probably been enjoying the relatively dry conditions this winter. If, however, you are a farmer who’s livelihood depends on a maintaining a certain balance of moisture within the soil you grow crops or grass on, your perspective may be different.

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"So, what are the causes of these drier conditions this winter? According to Paul Moore in Met Éireann, early December 2022 "saw very cold arctic air masses dominating, with high pressure to the north and the Jetstream displaced well to the south of Ireland, leading to drier than average conditions". Low pressure systems dominated during late December and early January, bringing with them wetter conditions, while the second half of January and most of February was characterised by much drier, milder conditions.

The reason for this change was a combination of milder air moving in from the West, while a high pressure system grew to the South. Generally speaking, high pressure in winter is associated with settled, fair and dry weather, which was the case for most of February. So, have we been lucky with the weather this winter? Well, this has been an unusual winter in that there were no named storms affecting Ireland, which certainly has been good news for most.

Ireland usually gets a ton of rain every year - does this mean we'll pay for it in the next few months?

"According to Dr Sandra Spillane from Met Éireann, ‘one thing we can always be sure of, rain will fall again in Ireland’. A below average amount of rainfall during the winter does not act as an indicator for the following season’s rainfall and a dry Winter is not a forecast for a dry Spring. If you want an actual forecast, you can always get up-to-date forecasts on Met.ie!

"Met Eireann climatologist, Paul Moore explains that a Sudden Stratospheric Warming (SSW) began on February 16th and is still ongoing, which adds a high degree of uncertainty to the overall forecast for the next month. The SSW in February 2018 led to the 'Beast from the East' and Storm Emma, while the SSW in January 2019 had no significant impact here in Ireland.

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"So what does that mean in a nutshell? While an SSW can be significant in terms of the weather we experience here in Ireland, its occurrence does not guarantee any particular set of weather conditions going forward. But impacts from the SSW were felt during the first week of March, when a cold Arctic air mass swept down over the country, which led to significant snowfall in places between March 8th and 10th, three weeks after the start of the SSW.

Is the lack of rain over the winter months an indicator of drought conditions ahead?

"While the occurrence of lower-than-average rainfall can precipitate (pun intended!) drought conditions, a dryer than average Winter does not mean that the Spring will be drier than normal. The infographic below provides meteorological definitions surrounding drought conditions and will provide a bit of context for the commentary below.

"There were nine dry spells at nine different stations between Monday 16th January and Tuesday 14th February 2023, lasting between 16 and 30 days. There was one absolute drought at Johnstown Castle, Co Wexford which started on Wednesday 25th January and lasted for 16 days and two partial droughts in County Dublin, at Dublin Airport (31 days) and the Phoenix Park (30 days).

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"It is worth noting, that these definitions for meteorological dry periods exist along a drought spectrum, which also includes hydrological drought (which affects our water supply) and agricultural drought (which impedes plant growth). Thankfully, this past winter has not experienced either of these types of droughts, but current climate models suggest changes ahead. As our climate changes into the future, model projections suggest that there will be an increase in the number of extended dry periods as well as projected decreases in rainfall, particularly during the summer months in Ireland.

What's our average rainfall like?

"Past weather statements from Met Éireann provide context for different weather events. The LTA or 'normal range’ for rainfall helps to put rainfall events into context, which is important because rainfall is a key indicator of changes in climate. This highlights the importance of having high quality observations to assess the effects of climate change on the water cycle."

What will our rainfall look like in the future?

"The extent to which Ireland’s climate will change as a result of increasing levels of greenhouse gas concentration in the atmosphere, is estimated using climate models. Due to the uncertainty involved in estimating future emissions, these models are ran using different ‘scenarios’, each of which assumes lower or higher concentrations of greenhouse gas.

"The most recent iteration of these scenarios include alternative socioeconomic developments to derive different levels of future GHGs for the climate models to use. This means that climate models provide ranges of how variables like precipitation and temperature will change as the century progresses. While there is uncertainty implicated in these ranges, overall rainfall is projected to become more variable into the future, with increases in the frequency of both heavy precipitation events and dry periods."